Communication apparatus

ABSTRACT

A communication apparatus has an A/D converter which converts an analog signal which was received, into a digital signal, a converter which converts a reception signal so as to enable handling of phase information, a carrier detector which detects presence or absence of the reception signal, a synchronous circuit which extract synchronization timing from the reception signal, an equalizer which corrects the reception signal so as to cancel influence of a transmission path, a transmission path estimator which estimates a state of a power line transmission path, and a judging unit which judges the reception signal, which was amended by the equalizer, by use of a threshold value.

BACKGROUND OF THE INVENTION

This invention relates to a communication apparatus and a communicationmethod using multi-carrier transmission system, particularly, to acommunication apparatus and a communication method which used amulti-carrier transmission system (Digital Wavelet Multi Carriertransmission system, hereinafter, referred to as DWMC transmissionsystem) which carries out data transmission by digital modulation anddemodulation processing which used a real coefficient wavelet filterbank which is more suitable for a power line transmission path and atransmission path such as a telephone line.

As a conventional technology which has been frequently used in themulti-carrier transmission system, there are FFT (Fast FourierTransform) based OFDM (Orthogonal Frequency Division Multiplexing) andWavelet based OFDM. Such an example that these technologies were appliedto power line communication is disclosed in (JP-A-11-163807). Thewavelet base has a resistance property to inter-carrier interferencesince a side Lobe of an amplitude spectrum is low, and is of anexcellent characteristic. In addition, in order to avoid collapse oforthogonality, in the FFT based OFDM, GI (guard inverval) isindispensable, while in the wavelet based OFDM, it is not necessary.This improves transmission efficiency. Since processing of the FFT basedOFDM is known well, an explanation will be omitted. Since the waveletbased OFDM is digital modulation and demodulation processing which useda real coefficient wavelet filter bank, it is a multi-carrier system ofa kind, and is a thing which generates a transmission signal bycombining a plurality of digital modulation waves by the realcoefficient filter bank. As a modulation system of each carrier, PAM(Pulse Amplitude Modulation) is used. Data transmission by a DWMCtransmission system is transmitted in such a manner that an impulseresponse of each sub carrier is overlapped in each sub carrier as shownin FIG. 20. Each transmission symbol becomes such a time wave that animpulse response of each sub carrier was combined as shown in FIG. 21.An example of the amplitude spectrum is shown in FIG. 22. In the DWMCtransmission system, approximately tens of hundreds of˜transmissionsymbols of FIG. 20 are collected to configure one transmission frame. Aconfiguration example of a DWMC transmission frame is shown in FIG. 23.In this DWMC transmission frame, in addition to an information datatransmission symbol, a preamble symbol etc., which are used for carrierdetection, synchronization, equalization and so on, are included. Aconceptual configuration of a power line communication apparatus in casethat the DWMC transmission system was adopted is shown in FIG. 19.Firstly, in a transmitting device 299, bit data is converted into symboldata by a symbol mapper 210, and in accordance with each symbol data,symbol mapping (PAM) is carried out. And, in a serial-parallel converter220, a real value di (i=1˜M) is given with respect to each sub carrier,and in an inverse wavelet conversion part 230, inverse waveletconversion is carried out on a time axis. By this, a sample value of atime axis waveform is generated, and a sample value sequence, whichrepresents a transmission symbol, is generated. In a D/A converter 240,it is converted from this sample value sequence to a base band analogsignal waveform, which is continued in terms of time, and transmitted.In a receiving device 399, a reception signal is converted into adigital signal in an A/D converter 310, and wavelet-converted so as tobe able to handle phase information in a complex wavelet converter 320,and in a carrier detector 330, presence or absence of the receptionsignal is detected, and in a synchronous circuit 340, synchronizingtiming is extracted from the reception signal, and in an equalizer 350,the reception signal is compensated so as to cancel influence of atransmission path, and in a transmission path estimator 370, a state ofa power line transmission path is estimated, and in a judging unit 380,the reception signal is judged by use of a threshold level. Here, thenumber of pieces of the sample values on a time axis, which aregenerated by inverse wavelet conversion, is normally 2^(n) (n is apositive integer) pieces.

In the meantime, in a conventional system, there was such a problem thattransmission path estimation, which is carried out in a receivingdevice, can not follow sufficiently to instantaneous fluctuation andperiodical fluctuation of wide-band noise or narrow-band noise, orinstantaneous fluctuation and periodical fluctuation which come up withamplitude fluctuation and phase fluctuation of a transmission pathitself, when transmission path estimation is simply carried out onlyonce in a certain cycle, in a power line transmission path. Here, as oneexample of the power line transmission path, an attenuationcharacteristic of the power lien transmission path is shown in FIG. 24.In addition, FIG. 25 is a view which shows a group delay characteristicof the power line transmission path.

As described above, in a multi-carrier power line communicationapparatus which used the conventional wavelet, it has such a problemthat transmission path estimation, which is carried out in a receivingdevice, cannot follow sufficiently to instantaneous fluctuation andperiodical fluctuation of wide-band noise or narrow-band noise, orinstantaneous fluctuation and periodical fluctuation which come up withamplitude fluctuation and phase fluctuation of a transmission pathitself, when transmission path estimation is simply carried out onlyonce in a certain cycle, in a power line transmission path. In thispower line communication apparatus, it is requested to sufficiently takehold of a transmission path state, and to heighten transmissionefficiency.

SUMMARY OF THE INVENTION

This invention is to provide a communication apparatus which solves theabove-described problem, and which sufficiently takes hold of a powerline transmission path characteristic, and which follows to varioustransmission path fluctuation, and which can heighten transmissionefficiency.

This invention is a communication apparatus which carries outmulti-carrier modulation processing, and a receiving device is equippedwith an A/D converter which converts an analog signal which wasreceived, into a digital signal, a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal, acarrier detector for detecting the reception signal, a synchronouscircuit for being synchronized with the reception signal, an equalizerfor compensating a distorted signal due to influence of a transmissionpath, a noise detector which detects presence or absence of narrow-bandnoise in each sub carrier band by use of a signal which was converted bythe converter, a transmission path estimator which determines amulti-value level of primary modulation which is used by each subcarrier of a symbol mapper in a transmitting device, by use of a signalwhich is outputted from the equalizer and information of presence orabsence of the narrow-band noise which is outputted from the noisedetector, and a judging unit which carries out judgment by use of thesignal which is outputted from the equalizer.

By this, it becomes possible to sufficiently follow to variousfluctuations of a transmission line such as a power line transmissionpath, and as a result, it becomes possible to heighten transmissionefficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram which shows a receiving device in anembodiment 1 of this invention.

FIG. 2 is a view which shows a scatter of an equalizer output signal.

FIG. 3 is a view which shows a noise characteristic in a power linetransmission path.

FIG. 4 is a block diagram which shows a receiving device in anembodiment 2 of this invention.

FIG. 5 is a view which shows a noise characteristic in such a case thatwide-band noise was added in a power line transmission path.

FIG. 6 is a frame configuration view for explaining an operation of anormal transmission path estimator.

FIG. 7 is a frame configuration view in such a case that transmissionpath estimation is carried out by use of time of a power supply cycle.

FIG. 8 is a block diagram of a receiving device in an embodiment 5 ofthis invention.

FIG. 9 is a frame configuration view in such a case that transmissionpath estimation is carried out by use of a transmission path estimationexclusive use frame and a data frame.

FIG. 10 is a graph which shows CINR in such a case that there was almostno transmission path fluctuation in case that transmission pathestimation was carried out at a plurality of times.

FIG. 11 is a graph which shows CINR in such a case that there istransmission path fluctuation in case that transmission path estimationwas carried out at a plurality of times.

FIG. 12 is a view of an amplitude spectrum in a DWMC transmissionsystem.

FIG. 13 is a pattern diagram of a level of a signal which was received.

FIG. 14 is a pattern diagram at the time when a gain of an amplifier ofa transmitting device was lowered by only 30 dB.

FIG. 15 is a pattern diagram of a level of a signal which is received atthe time when gains of sub carriers up to sub carrier number 1˜100 werelowered by only 6 dB.

FIG. 16 is a pattern diagram of a level of a signal which is received atthe time when gains of sub carriers up to sub carrier number 1˜100 werelowered by 12 dB, and gains of sub carriers up to sub carrier number101˜200 were lowered by only 6 dB.

FIG. 17 is a pattern diagram of a level of a signal which is received atthe time when gains of sub carriers up to sub carrier number 1˜100 werelowered by 18 dB, and gains of sub carriers up to sub carrier number101˜200 were lowered by 12 dB, and gains of sub carriers up to subcarrier number 201˜300 were lowered by only 6 dB.

FIG. 18 is a pattern diagram of a transmission path estimationcharacteristic in such a case that a dynamic range is insufficient.

FIG. 19 is a view which shows a power line communication apparatus in aconventional system.

FIG. 20 is a view which shows a wavelet waveform example.

FIG. 21 is a view which shows a transmission waveform example in theDWMC transmission system.

FIG. 22 is a view which shows a transmission spectrum example in theDWMC transmission system.

FIG. 23 is a view which shows a configuration example of an inside of atransmission frame in the DWMC transmission system.

FIG. 24 is a view which shows an attenuation characteristic of a powerline transmission path.

FIG. 25 is a view which shows a group delay characteristic of a powerline transmission path.

FIG. 26 is a view which shows a frame configuration example of acommunication apparatus in an embodiment 22 of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of this invention will be described withreference to FIG. 1 to FIG. 18.

FIG. 1 is a block diagram which shows a receiving device in anembodiment 1 of this invention. In passing, a transmitting device is thesame as the transmitting device 299 of FIG. 19, as to which anexplanation was carried out in the conventional technology.

In FIG. 1, 310 designates an A/D converter which converts an analogsignal into a digital signal, and 320 designates a complex waveletconverter which generates a in-phase signal and an orthogonal signal bywavelet-converting a reception signal, and 330 designates a carrierdetector for detecting a transmission signal which is transmitted from atransmitting device, and 340 designates a synchronous circuit forsynchronizing with the reception signal, and 350 designates an equalizerfor compensating a signal which was distorted by influence of atransmission path, and 360 designates a noise detector which detectspresence or absence of narrow-band noise in each sub carrier band, byuse of a signal after complex wavelet conversion, and 370 designates atransmission path estimator which determines primary modulation which isused in each sub carrier of a symbol mapper in a transmitting device, byuse of a signal which is outputted from the equalizer 350 andinformation of presence or absence of narrow-band noise which isoutputted from the noise detector, and 380 design at esa judging unitwhich carries out judgment by use of a signal which is outputted fromthe equalizer 350.

As to the receiving device which was configured in this manner, itsoperation will be described by use of FIG. 1 to FIG. 3.

FIG. 2 is a view which shows a scatter of an equalizer output signal,and FIG. 3 is a view which shows a noise characteristic in a power linetransmission path.

In FIG. 1, a reception signal is converted from an analog signal into adigital signal in the A/D converter 310, and in the complex waveletconverter 320, a digital signal, which was received, iswavelet-converted, and in the carrier detector 330, a signal, which istransmitted from the transmitting device, is detected, and in thesynchronous circuit 340, wavelet conversion timing is adjudted of thecomplex wavelet converter 320, so as to be synchronized with a receptionsignal by use of a preamble signal, and in the equalizer 350, influenceof a transmission path is removed, and in the noise detector 360,narrow-band noise, which exists in a use band, is detected, and in thetransmission path estimator 370, a state of a transmission path isestimated, and a primary modulation system of a symbol mapper which isused in the transmitting device is determined, and in the judging unit380, judgment is carried out by use of a signal which is outputted fromthe equalizer 350.

FIG. 2 shows a scatter (all sub carrier portions) of an equalizer outputof the receiving device in case that all sub carriers 2PAM were selectedin the symbol mapper of the transmitting device. Generally, in case ofcarrying out transmission path estimation, a well-known frame is made tobe transmitted from the transmitting device for the purpose oftransmission path estimation, and in the transmission path estimator 370of the receiving device, CINR (Carrier power to(Interference-plus-Noise) power Ratio) is measured with dispersion fromsignal point allocation (in case of 2PAM, ±1) as a noise amount inaccordance with the output from the equalizer 350. By use of CINR whichwas measured in each sub carrier, primary modulation (e.g., 16PAM, 8PAMetc.), which is used in each sub carrier, is selected, and informed tothe transmitting device 299. This is transmission path estimation whichis normally carried out in the transmission and receiving device.

Here, such a case that a communication system of this invention wasapplied to power line communication will be described. In the power linecommunication, as a band which can be used, 2 MHz to 30 MHz is beingconsidered. FIG. 3 shows a noise characteristic in a band which is usedfor the power line communication. Since this band is used for amateurradio and short wave broadcasting etc., in addition to the power linecommunication, those existing systems exist as narrow-band noise to thepower line communication, as shown in FIG. 3. In case that thesenarrow-band noises exist on a steady basis, since CINR is deterioratedin a certain sub carrier at the time of transmission path estimation, itis possible to deal with, by making a sub carrier, which is using thesame band as that band, non-use. In addition, if these narrow-band noiselevels exist at a noise level or less, which was obtained at the time oftransmission path estimation, on a steady basis, even if narrow-bandnoise does not exist, CINR is not deteriorated, and therefore, it doesnot become a problem.

However, when there is such a case that these narrow-band noises appearsand disappears on an irregular basis and become larger than a noiselevel at the time of transmission path estimation, it becomes unstablein such a manner that there is an error or there is not an error untilthe time of transmission path estimation which will be carried out next,and even in case that error correction was carried out, in the worstcase, there becomes such a state that a frame retransmission request hasto be carried out, which results in dropping down transmissionefficiency.

For the purpose of avoiding the suchlike thing, as shown in FIG. 1,noise detection is carried out by the noise detector 360. In addition tothe output of the equalizer 350, this detection result is also used asinformation for estimation by the transmission path estimator 370. Theway to deetct noise detection is concretely explained. In the complexwavelet converter 320, wavelet conversion is carried out, and when anoutput in each sub carrier is measured, as shown in FIG. 3, signalsincluding narrow band noise are outputted from the complex waveletconverter 320.

Here, the noise detector 360 obtains an average value, median or thelike of all sub carriers, checks a sub carrier, which has a large valueof for example, 12 dB or more, detects such sub carrier as “havingnarrow band noise” and transfers this information to the transmissionpath estimator 370. In case that the system becomes unstable, thetransmission path estimator inhibits to use of the sub carrier which waschecked here.

In addition, by use of an output of the complex wavelet converter 320,the carrier detector 330, the synchronous circuit 340, and the equalizer350 are controlled, and in these blocks, an average value etc. areobtained through the use of values of all sub carriers, and thereby,processing is carried out. In this case, when narrow-band noise of ahigh level is inputted and processed in those circuits, it isconceivable that a characteristic is deteriorated to a large extent. Onthat account, it is possible to maintain high performance by making asub carrier, which was checked in the noise detector 360, non-use inthese circuits.

By these configurations, in case that this system was applied to thepower line communication, it is possible to mitigate influence ofnarrow-band noise which is received from another system, and goodtransmission path estimation becomes possible, and in addition, it ispossible to also improve carrier detection and synchronization accuracy.

As mentioned above, the communication apparatus of the present inventionis explained as the power line communication. The power linecommunication is one example of the transmission line which causesirregularly the narrow band noises. Thus, the present invention is notlimited to the power line communication.

In passing, in the embodiment 1, the complex wavelet converter 320 isused, but a communication apparatus of this invention is not restrictedto this, and it is possible to apply to such a wavelet converter that aphase of each sub carrier can be confirmed.

In case that there occurs no phase lag in each sub carrier, it ispossible to apply, such a wavelet converter by which an in-phase signalis obtained, to a communication apparatus of this invention.

(Embodiment 2)

FIG. 4 is a block diagram which shows a receiving device in anembodiment 2 of this invention. In passing, a transmitting device is thesame as the transmitting device 299 of FIG. 19.

In addition, a difference between the receiving devices of FIG. 4 and ofFIG. 1 is only an AGC (Automatic Gain Control) circuit 390. Since othercircuits are the same as the circuits which were explained in FIG. 1,descriptions are pursuant to the descriptions in the embodiment 1. 390designates an AGC circuit which automatically adjust a gain of areception signal. Next, by use of FIG. 4 and FIG. 5, an operation incase that this system was applied to the power line communication willbe described. FIG. 5 is a view which shows a noise characteristic incase that wide-band noise was added in a power line transmission path.

A difference from the embodiment 1 is to carry out noise detection bythe noise detector 360 including a gain which is used by the AGCcircuit.

In the embodiment 1, presence or absence of narrow-band noise can bedetected, and in addition to this detection, by detecting a gain of theAGC circuit, it becomes possible to know influence of wide-band noise,which could not be known in this embodiment 1. FIG. 5 shows an amplitudespectrum of a power line transmission path by presence or absence of anelectric equipment which continuously generates impulse noise of a highlevel in a time axis.

Concretely speaking, by turning ON an electric equipment which generatesimpulse noise of a high level in a time axis, a noise level is increasedin all bands (from 2 MHz to 30 MHz), which seem to be used in power linecommunication. In the suchlike case, since it is not possible to judgepresence or absence of wide-band noise in the embodiment 1, presence orabsence of wide-band noise is judged by use of a gain of the AGC circuit390, in the receiving device in this embodiment 2.

By this system, it is possible to detect narrow-band noise and wide-bandnoise, and in case that it was detected, by carrying out transmissionpath estimation in tune with the number of retransmission etc., itbecomes possible to carry out good communication in a very bad powerline communication transmission path.

For example, even in case that there is no narrow-band noise, whichmakes a sub carrier, in which narrow-band noise exists on an irregularbasis, non-use, the noise detector 360, considering that a system hasbecomes unstable due to random wide-band noise when wide-band noiseexists by an output from the AGC circuit 390 and retransmission occursfrequently in normal transmission path estimation, mitigates a thresholdvalue which is used for transmission path estimation and transmissionpath estimation is carried out at a plurality of times, and, in thatstate, determines primary modulation of each sub carrier by using aminimum CINR value in each sub carrier. By doing in this manner, evenunder a power line communication transmission path in which variousnoises exist, it becomes possible to carry out good communication.

In case that this system was applied to power line communication, by acommunication apparatus which is described in the embodiment 2 of thisinvention, it is possible to reduce influence of narrow-band noise whichis received from another system, and mitigated is influence of wide-bandnoise due to impulse noise of a high level at a time axis, which isemitted from an electric equipment etc., and good transmission pathestimation becomes possible.

(Embodiment 3)

A transmission path estimator in an embodiment 3 of this invention willbe described. In this embodiment, a receiving device, and a transmittingdevice of a communication apparatus are the same as in the embodiment 1or 2.

FIG. 7 shows a frame configuration view in case of carrying outtransmission path estimation by use of time of a power supply cycle.

Next, an operation will be described. FIG. 6 shows a frame configurationview for explaining an operation of a normal transmission pathestimator.

Normally, as shown in FIG. 6, a transmission path estimation frame isadded in a frame to be transmitted and received (in the figure, a “CEframe” is the “transmission path estimation frame”).

Generally speaking, in a transmission path estimating method of thesuchlike configuration, this transmission path estimation frame is usedagain on an irregular basis, when a transmission path fluctuatessignificantly, and if a past transmission path estimation result isused, many errors will be generated, and as a result, it comes to be insuch a state that retransmission occurs frequently.

Or, since efficiency is bad if transmission path estimation is carriedout after retransmission occurs frequently, there is also such a casethat certain maximum time has been determined, and transmission pathestimation is carried out in tune with its cycle.

In FIG. 6, to instantaneous fluctuation of a transmission path, it ispossible to cope with it by carrying out re-transmission pathestimation, since judgment errors arise in case that it is differentfrom a past transmission path estimation result significantly, and itresults in retransmission occurring frequently, but, for example, incase that instantaneous fluctuation of a transmission path arises insynchronization with a power supply cycle (in case of 50 Hz, 20 ms) orits half cycle (in case of 50 Hz, 10 ms), if re-transmission pathestimation is carried out on each occasion, transmission efficiency willbe deteriorated significantly.

In order to avoid the suchlike deterioration, as shown in FIG. 7, thetransmission path estimator 370 in the embodiment 3 of this inventioncarries out an operation of transmission path estimation for a powersupply cycle 1 cycle portion, for example, by use of a transmission pathestimation frame continuously during a period of a power supply cycle.

As a result of that, it is possible to improve entire transmissionefficiency by carrying out such things that, taking hold of which timingfluctuation due to noise and transmission path fluctuation weregenerated at, in that zone, it is made to not send out a signal, or itis made to lower a multi-value level of primary modulation, or frequencyand time diversity is carried out to make that frame hold a resistanceproperty.

In addition, to fluctuation which arises at a different cycle, there isa necessity to carry out transmission path estimation in tune with thecycle. Further, it is also possible to carry out transmission pathestimation randomly, but not continuously, by making such a state thattotal transmission path estimation time becomes nearly 1 cycle portion.

By the suchlike configuration, for example, to fluctuation of noise andtransmission path fluctuation which were synchronized with a powersupply cycle, it becomes possible to make a prediction, and it becomespossible to receive and to transmit a signal effectively.

(Embodiment 4)

The transmission path estimator 370, which is used in a communicationapparatus in an embodiment 4 of this invention, will be described.

In this embodiment, by use of the configuration/operation of thecommunication apparatus of the embodiment 3, transmission pathestimation is carried out in a certain cycle.

Further additionally, the transmission path estimator 370 in thisembodiment, in case that, at that time, fluctuation of noise andfluctuation of a transmission path exist in 1 cycle, but in each subcarrier, influence of transmission path fluctuation is smaller than athreshold value (in case that it does not have influence on errors),becomes to maintain good transmission efficiency by use of that subcarrier even if there is fluctuation.

By realizing the suchlike configuration, as compared to thecommunication apparatus in the embodiment 3, it becomes possible tofurther heighten transmission efficiency.

(Embodiment 5)

A transmission path estimator in an embodiment 5 of this invention willbe described.

A block diagram of a receiving device in the embodiment 5 of thisinvention is shown in FIG. 8.

In passing, the transmitting device 299 is to use the same thing as inFIG. 19.

As to blocks which are being used, since blocks with the same numbersbecome to be of the same explanations as things which were explained inthe embodiments 1, 2 etc., explanations will be omitted.

A point on which this embodiment is different from a conventional systemis such a point that a judgment signal from the judging unit 380 isinputted to the transmission path estimator 370.

Normally, as shown in FIG. 6, prior to communication start etc.,transmission path estimation is carried out once, and next transmissionpath estimation will be carried out in case that a transmission pathfluctuated significantly, and in case that it exceeded maximum time of acycle for carrying out transmission path estimation, and so on. It isnormal to use an exclusive use frame as a transmission path estimationframe in this case.

However, transmission efficiency is deteriorated depending on the numberof transmission path estimations. Thus, in this system, by configuringthe transmission path estimator 370 and the judging unit 380 as acircuit configuration of a judgment feed-back type, in CINR which isobtained at the time of transmission path estimation, dispersion from ajudgment value in each sub carrier is obtained as CINR, and thereby,transmission path estimation is to carried out not only in atransmission path estimation frame but also in a normal data frame.

FIG. 9 is a frame configuration view in case of carrying outtransmission path estimation by use of a transmission path estimationexclusive use frame and a data frame.

It is conceivable that there occurs a difference between a result oftransmission path estimation which was carried out because oftransmission path fluctuation at the time of communication start, andtransmission path estimation which is carried out in a data frame. Atthis time, in case that a difference occurred with such a degree that anerror is generated in a result of transmission path estimation which wasmeasured in a transmission path estimation frame, and a result oftransmission path estimation which was measured in a data frame,updating of a transmission path estimation result is requested to thetransmitting device 299 side, and thereby, a transmission pathestimation result is updated. In case of updating, a result, which wasobtained in the data frame, may be used. Transmission path estimationmay be carried out by using an exclusive use frame again. In passing,the judgment feed back type circuit configuration of the receivingdevice of this embodiment is applicable also to the receiving device ofthe embodiment 1 or 2.

By the suchlike configuration, it is possible to carry out transmissionpath estimation by use of a normal transmission path estimationexclusive use frame and a data frame, and therefore, as a result, it ispossible to heighten transmission efficiency.

(Embodiment 6)

A transmission path estimator, which is used in a communicationapparatus in an embodiment 6 of this invention, will be described. Here,as a configuration of a communication apparatus, used is theconfiguration of the communication apparatus of the embodiment 5. Apoint, which is different from the embodiment 5, is a transmission pathestimating method by use of a data frame of the transmission pathestimator 370.

In case of carrying out transmission path estimation, required is anaverage of a symbol, which is a target for averaging noise, or more (thenumber of necessary symbols is assumed to be S). However, there is nosuch guarantee that each data frame is composed of S symbol or more. Onthat account, a unit to be averaged is set to S symbol unit, but not aframe unit, and averaging is to be continued until reaching to the Ssymbol, even if a frame is changed.

Concretely speaking, a transmission path estimator carries out averagingin a form which is as follows.

Generally, a transmission path estimator 370 can complete transmissionpath estimation in 1 frame, if symbol number necessary for transmissionpath estimation is entered in 1 frame which is received by a receivingdevice.

However, if a frame, which is not for transmission path estimation butfor exchanging normal data, is used for transmission path estimation,there occurs such a case that only several symbols exist in payloaddata.

On that account, by use of a plurality of frames, arises a necessity tocarry out 1 time transmission path estimation which corresponds to sucha case that a transmission path estimation exclusive use frame was used.

For example, assuming that 1 frame is configured of a preamble signalnecessary for control of a receiving device and a payload data signalfor sending information, when the number of symbols necessary fortransmission path estimation is assumed to be 128, the number of symbolsin payload data which is included (can be used for transmission pathestimation) in a frame when communication is going on is assumed to be8.

In this case, a transmission path estimator becomes to be able to obtaina 128 symbol averaged transmission path estimation result (the samelevel as normal transmission path estimation) with 16×8=128, byreceiving 16 frames of a reception signal.

By the suchlike configuration, it is possible to carry out transmissionpath estimation by use of a data frame, in accordance with various framelength, and therefore, as a result, it is possible to heightentransmission efficiency.

(Embodiment 7)

A transmission path estimator 370 of a communication apparatus in anembodiment 7 of this invention will be described. As a blockconfiguration of the communication apparatus of this embodiment, used isthe block configuration of the communication apparatus which wasdescribed in the conventional system as shown in FIG. 19 or in theembodiment 5.

In this embodiment, since an operation of the transmission pathestimator 370 of a receiving device in the communication apparatus isdifferent from that of another embodiment, the operation will behereinafter described.

In communication which uses a power line as a transmission path, as to ause band in an existing system, only a portion (e.g., amateur radio useband) is made to be always non-use. In other bands than it, it is normalto not send out a signal as to a sub carrier which became non-use by atransmission path estimation result.

However, if nothing is done, in case of carrying out transmission pathestimation in a data frame, it is not possible to carry out transmissionpath estimation in a sub carrier which is of non-use. Thus, even in thesuchlike sub carrier, pseudo data is given, and thereby, transmissionpath estimation is made to be carried out in a data frame.

Since judgment data of a judgment feed-back type is used in a dataframe, as to the pseudo data here, it is convenient to fix a multi-valuelevel, and it is good to use a minimum multi-value level (e.g., 2PAM)from the view point of a resistance property.

By the such like configuration, it becomes possible to carry outtransmission path estimation by use of a data frame, even in a subcarrier which became non-use by a transmission path estimation result,and as a result, it become possible to heighten transmission efficiency.

(Embodiment 8)

A transmission path estimator of a communication apparatus in anembodiment 8 of this invention will be described. As to a blockconfiguration of the communication apparatus of this embodiment, used isthe block configuration of the communication apparatus which isdescribed in the embodiment 1, 2 or 5, and as an operation of thetransmission path estimator 370, transmission path estimation is carriedout at a plurality of times.

As an operation of the transmission path estimator 370 in case ofcarrying out transmission path estimations at a plurality of times, howto determine a transmission path estimation value will be shown.

Transmission path estimation of the transmission path estimator 370 iscarried out by measuring CINR in each sub carrier in a reception signal,but since a transmission path fluctuates periodically ornon-periodically, in case of a transmission path such as a power line,in case that transmission path estimation was carried out at a pluralityof times, a transmission path estimation value of each sub carrier showsalmost the same value, and fluctuates significantly.

FIG. 10 is a graph which shows CINR in case that there was almost notransmission path fluctuation in case that transmission path estimationwas carried out at a plurality of times.

In case of FIG. 10, there is simply influence due to only backgroundnoise such as Gauss noise. In this case, it is preferable that thetransmission path estimator 370 uses a maximum value in each sub carrieras an initial value, to a result which was obtained by transmission pathestimations at a plurality of times, and uses a median in case thatretransmission from the transmitting device 299 becomes to occur at manytimes, and uses a minimum value if communication does not become stable.

Here, as to the median, since calculation such as SORT becomes enormous,a difference (e.g., 2 dB) of the maximum value and the median has beenobtained statistically, and by utilizing that value and the maximumvalue, it is also possible to obtain a result which is equivalent tothat at such time that the median was used.

By realizing the suchlike configuration, it becomes possible to maintaintransmission efficiency at the highest level in tune with eachtransmission path.

(Embodiment 9)

The transmission path estimator 370 of a communication apparatus in anembodiment 9 of this invention will be described. A block configurationof the communication apparatus in this embodiment is the same blockconfiguration as that described in the embodiment 8. In this embodiment,as a transmission path for which the transmission path estimator 370estimates, considered is almost the same transmission path as thetransmission path which was considered in the embodiment 8.

As a point which is different from the embodiment 8, it is on such apoint that considered is such a case that background noise is not Gaussdistribution, and also, depending on an attenuation characteristic of atransmission path (e.g., such a case that CINR values of many subcarriers exist in the vicinity of a threshold value, etc.), as athreshold value, which is used when a primary modulation system to beused in a symbol mapper of a transmitting device from CINR which wasobtained by transmission path estimation, a value which is set up in thebeginning becomes improper.

The transmission path estimator 370 in this embodiment, on the basis ofthe above-described knowledge, controls in such a manner thattransmission efficiency in an entire system including retransmissionetc. is improved, by changing setup of each threshold value higher (i.e.by setting them to have a margin). This is because there is such a casethat, depending on a distribution of CINR, transmission efficiency ischanged significantly by simply changing a threshold value. By thesuchlike configuration, it becomes possible to further heightentransmission efficiency, more than that of the communication apparatusin the embodiment 8.

(Embodiment 10)

The transmission path estimator 370 of a communication apparatus in anembodiment 10 of this invention will be described. In this embodiment,considered is a transmission path which is almost the same as thetransmission path which was considered in the embodiment 8. As a pointwhich is different from the embodiment 8, it is on such a point that atransmission path characteristic fluctuates significantly, in case thata plurality of transmission path estimation results, which wereobtained, were viewed. In FIG. 11, shown is a graph which shows CINR incase that there is transmission path fluctuation in case thattransmission path estimation was carried out at a plurality of times. Inthe suchlike transmission path, every time transmission fluctuationoccurs, errors are increased, depending on its range, and there is sucha possibility that, even if error correction is carried out, a frame atthat time becomes to be retransmitted.

Thus, the transmission path estimator 370 in this embodiment, on thebasis of the above-described knowledge, can control in such a mannerthat transmission efficiency in an entire system includingretransmission etc. is improved, by making non-use to such a sub carrierthat its fluctuation is large, to CINR which was obtained in each subcarrier, or by reducing retransmission by selecting a minimum value inresults which were obtained.

By the suchlike configuration, it becomes possible to further heightentransmission efficiency, more than that of the embodiment 8.

(Embodiment 11)

The transmission path estimator 370 of a communication apparatus in anembodiment 11 of this invention will be described. In this embodiment,considered is a transmission path which is almost the same as thetransmission path which was considered in the embodiment 10.

As a point which is different from the transmission path of theembodiment 10, it is on such a point that transmission path fluctuationoccurs in synchronization with a power supply cycle or its half cycle,by use of a power line as a transmission path.

In a transmission path as shown in FIG. 11, every time transmission pathfluctuation occurs, errors are increases, depending upon its range, andthere is such a possibility that, even if error correction is carriedout, a frame at that time becomes to be retransmitted.

At this time, to a request of transmission path estimation, when it isprocessed by 1 time transmission path estimation, there is such apossibility that it is estimated lower than true transmission pathcapacity, depending on transmission path estimation timing. In thiscase, as a system, it may operate stably, but a transmission speedslows.

Under such an environment that a buffer etc. are sufficiently providedon a upper layer and influence due to retransmission may not beconsidered, it is desirable that a transmission path estimation resultis obtained at a level which is close to the true transmission pathcapacity if possible.

Thus, the transmission path estimator 370 in this embodiment, on thebasis of the above-described knowledge, is designed to carry outtransmission path estimation 2 times with timing which is notsynchronized with a power supply cycle or its half cycle, to atransmission path estimation request, and to select a value in whichCINR is larger, in each sub carrier, by utilizing a transmission pathestimation result which was obtained. By this, as to at least 1 timeamong 2 times of transmission path estimations, it is possible to carryout transmission path estimation without stumbling across transmissionpath fluctuation which was synchronized with a power supply cycle. Inaddition, since a better result of CINR is taken in each sub carrier, atransmission speed is maintained at a high level.

By the suchlike configuration, it is possible to carry out goodtransmission path estimation, even under such a power line transmissionpath environment that there is transmission path fluctuation which wassynchronized with a power supply cycle, by simple processing.

(Embodiment 12)

The transmission path estimator 370 of a communication apparatus in anembodiment 12 of this invention will be described. In this embodiment,considered is a transmission path which is almost the same as thetransmission path which was considered in the embodiment 10.

FIG. 23 is a view which shows a configuration example of an inside of atransmission frame in a DWMC transmission system.

It is assumed that a frame configuration of a reception signal istransmitted by a frame which is composed of a preamble signal necessaryfor synchronization and equalization processing and a signal forinformation as in FIG. 23. Normally, it is understood that condition ofa power line transmission path changes vary slowly, as compared to awireless transmission path. In addition, as instantaneous fluctuation,it is generated by ON/OFF of an electric equipment, and soon. Further,transmission path fluctuation which was synchronized with a powersupply, and so on, are also conceivable.

The transmission path estimator 370 in this embodiment, on the basis ofthe above-described knowledge, is enough if it carries out transmissionpath estimation in a manner of a long cycle (at an interval from secondto minute), to very slow transmission path fluctuation, and has anecessity to carry out re-transmission path estimation since atransmission path state changes significantly, to instantaneousfluctuation due to ON/OFF of an electric equipment. Since it is possibleto predict where periodic fluctuation of a transmission path occurs, byuse of the communication apparatus of the embodiment 1 or 2, in the samemanner as in the embodiment 8, to periodic transmission path fluctuationwhich was synchronized with a power supply, it is possible to suppressan amount of data which is retransmitted although an overhead of apreamble is increased, by carrying out no signal transmission in thattime, or by finely dividing a frame.

By the suchlike configuration, since it is possible to reduce an amountof data to be retransmitted, it becomes possible to heightentransmission efficiency.

(Embodiment 13)

The transmission path estimator 370 of a communication apparatus in anembodiment 13 of this invention will be described. In this embodiment,as a block configuration of a communication apparatus, used is the blockconfiguration of the communication apparatus of the conventional systemof FIG. 19 or the embodiment 1 or 2.

In case of carrying out normal transmission path estimation, as shown inFIG. 10 and FIG. 11, CINR is obtained, and primary modulation, which isused in a symbol mapper of a transmitting device, is determined, andeach parameter is set up so as to transmit with maximum efficiency in atransmission path through which communication is carried out.

However, depending on a state, there is also such a case that it ispossible to carry out an operation of a system stably, by adaptivelygiving redundancy to a transmission system.

The communication apparatus of this embodiment carries out an operationas follows, on the basis of the above-described knowledge.

The transmission path estimator 370, in case that a transmission pathitself is not congested and in case that an amount of data to betransmitted is smaller than transmission path capacity (capacity whichwas obtained by transmission path estimation), is operated so as tolower by 1 rank (e.g., from 4PAM to 2PAM), to a multi-value level whichis judged in the vicinity of a threshold value, or to give a margin(e.g., 2 dB) to all threshold values, or further, to determine amulti-value level by use of a minimum value in case that transmissionpath estimation is carried out at a plurality of times.

Since these systems are designed so as to have a spectrum of a low sidelobe in each sub-carrier by use of wavelet conversion, they becomepossible because detailed CINR is obtained in each sub carrier by thetransmission path estimator 370.

In passing, this system is applicable not only to the waveletconversion, but also to muti-carrier communication which realizesanother low side lobe spectrum, by use of OFDM/OQAM (in this case, amulti-value level is MQAM: M is a multi-value number), Filtered OFDM,Filterred Mutitone systems etc.

In addition, this system is also applicable to a FET (Fast FourierTransform) based multi-carrier communication system in which acharacteristic is deteriorated but which has been often used since oldtimes.

By the suchlike configuration, it is possible to carry out optimizationin a total system including a transmission path, and furthermore, it ispossible to carry out stable communication.

(Embodiment 14)

The transmission path estimator 370 of a communication apparatus in anembodiment 14 of this invention will be described.

In this embodiment, as a block configuration of a communicationapparatus, used is the power line communication apparatus of theconventional system of FIG. 19 or the embodiment 1 or 2.

In case of carrying out normal transmission path estimation, as shown inFIG. 10 and FIG. 11, CINR is obtained, and primary modulation, which isused in a symbol mappter of a transmitting device, is determined, andeach parameter is set up so as to transmit with maximum efficiency in atransmission path through which communication is carried out.

However, depending on a state, there is also such a case that it ispossible to carry out an operation of a system stably, by adaptivelygiving redundancy to a transmission system.

The transmission path estimator 370 of this embodiment carries out anoperation as follows, on the basis of the above-described knowledge.

In case that a transmission path itself is not congested and in casethat an amount of data to be transmitted is smaller than transmissionpath capacity (capacity which was obtained by transmission pathestimation), by receiving information of types (Voip, data, Streamingetc.) of data to be sent from a upper layer, since there is no necessityof instancy in case of data such as a file etc. (although there is apossibility that retransmission occurs, since it is not data which isrequest for real-time, there is no problem.), communication is carriedout by a normal transmission system in consideration of maximumefficiency, and in addition, since instancy is important in Voipcommunication, on the assumption that stability is more important thanefficiency, it is conceivable that a multi-value level, which is closeto minimum, is made to be selected in each sub carrier if transmissionpath capacity is sufficient, or a resistance property is given to aframe itself by carrying out frequency diversity or time diversity, orfurther, since video images are transmitted in Streaming etc.,capacitance and instancy, which is not of a level of Voip, becomenecessary, and therefore, in this case, by realizing the very minimummulti-values in a form which was tuned with information which is desiredto be sent, a multi-value level of each sub carrier is determined.

These systems become possible since they are designed so as to have aspectrum of a low side lobe in each sub-carrier by use of waveletconversion, and detailed CINR is obtained in each sub carrier by atransmission path estimator. In passing, this system is applicable notonly to the wavelet conversion, but also to multi-carrier communicationwhich realizes another low side lobe spectrum, by use of OFDM/OQAM (inthis case, a multi-value level is MQAM: M is a multi-value number), etc.In addition, this system is also applicable to a FET (Fast FourierTransform) based multi-carrier communication system (for example, ADSL,802.11a and g) in which a characteristic is deteriorated but which hasbeen often used since old times.

By realizing the suchlike configuration, it is possible to carry outoptimization in a total system including a transmission path by carryingout transmission path estimation in consideration of an application, andfurthermore, it is possible to carry out stable communication.

(Embodiment 15)

The transmission path estimator 370 of a communication apparatus in anembodiment 15 of this invention will be described.

In this embodiment, as a block configuration of a communicationapparatus, used is the block configuration of the communicationapparatus of the conventional system of FIG. 19 or the embodiment 1 or2.

When a desired transmission speed was not satisfied in case thattransmission path estimation was carried out by a normal method, thereis such a possibility that it is not possible to take desired CINR onaccount of collapse of orthogonality of a wavelet filter bank due togroup delay of a transmission path.

-   -   normally, demodulation processing is carried out in a receiving        device, in synchronization with a reception signal, but it does        not mean that synchronization is realized to all sub carriers.

In short, on an actual transmission path, such a possibility thatcollapse of orthogonality occurs easily is high. In a transmission path,since a sub carrier, which is located in a band in which large groupdelay exists, is such a thing that collapse of orthogonality is large,large inter-carrier interference and inter-symbol interference occur. Asa result of that, in that band, since a interference wave exists, CINRis estimated to be low.

In order to solve this problem, in the communication apparatus of thisembodiment, a sub carrier, which can be used, is limited to, forexample, only a sub carrier which has an even number.

By this frequency utilization efficiency is lowered, but inter-carrierinterference due to collapse of orthogonality can be reducedsignificantly, and therefore, even if a sort of group delays exist, itis not almost affected by inter-carrier interference, and therefore,there is such a possibility that a transmission speed is improved as atotal system. In addition, since there occurs almost no overlap with anadjacent carrier, there is a resistance property to frequency deviation.

FIG. 22 is a view which shows a transmission spectrum example in a DWMCtransmission system.

By realizing a configuration as in FIG. 22, frequency utilizationefficiency is lowered, but in a transmission path in which group delaydeviation is large, inter-carrier interference can be reducedsignificantly, and in addition, there is a resistance property tofrequency deviation, and therefore, there is such a possibility that atransmission speed is improved as a total system.

(Embodiment 16)

The transmission path estimator 370 of a communication apparatus in anembodiment 16 of this invention will be described.

In this embodiment, as a block configuration of a communicationapparatus, used is the block configuration of the communicationapparatus of the conventional system of FIG. 19 of the embodiment 1 or2.

In case that a desired transmission speed is not satisfied in case thattransmission path estimation was carried out by a normal method, it isconceivable that a transmission path is in a very bad environment. Underthe very bad environment, transmission efficiency is lowered more indelay detection than synchronous detection, but since there is aresistance property, there exists such a case that it is desired to beused, but DWMC is Real modulation, and there is no phase in each subcarrier, and therefore, the delay detection is not possible.

However, there is such a method that delay detection by use of a phasebecomes possible even in DWMC, by giving redundancy to transmissiondata.

The transmission path estimator 370 in this embodiment, on the basis ofthe above-described knowledge, carries out an operation as follows.

In case that an impulse response length is assumed to be 4T (Trepresents a symbol cycle) of Wavelet (speaking of a filter length, 4M:M is the number of all sub carriers), data to be transmitted in each subcarrier is assumed to be the same in 4T zone. Transmission efficiencybecomes 0.25, but at the minimum, it is possible to handle the samephase as FET every 4T, and delay detection becomes possible.

This utilizes such a nature that, even in case of DWMC, if 4t continuedinformation is used, at the minimum, it becomes a sine wave every 4T. Asa matter of course, if an impulse response length of Wavelet becomes 8T,there is such a necessity that data to be transmitted in each subcarrier is made to be the same in 8T zone. In passing, because of such afact that it is possible to handle a phase, various technologies, whichare used in normal digital communication, becomes to be applicable toDWMC. Since transmission efficiency is deteriorated when theabove-described processing is carried out to all data, even by simplyusing for the very minimum portion, a system can be improved. Forexample, by applying only to a preamble signal and a pilot signal, it ispossible to improve system performance.

By realizing the suchlike configuration, redundancy is given toinformation which is desired to be sent, only by the same length as animpulse response length of Wavelet, and thereby, transmission efficiencyis deteriorated but a phase can be handled, and therefore, delaydetection becomes possible, and further, various technologies, which arebeing used in normal digital communication, can be applied to DWMC, andin addition, even in case that it is applied to a portion, it ispossible to improve system performance.

(Embodiment 17)

The transmission path estimator 370 of a communication apparatus in anembodiment 17 of this invention will be described.

In this embodiment, as a block configuration of a communicationapparatus, used is the block configuration of the communicationapparatus of the conventional system of FIG. 19 or the embodiment 1 or2.

In this embodiment, it is assumed that output power of the transmittingdevice 299 is smaller than maximum power, or maximum power required bythe law.

The communication apparatus, in case that it did not satisfy a desiredtransmission speed in case that transmission path estimation was carriedout by a normal method, calculates how much gain of an amplifier of thetransmitting device has to be increased so as to realize the desiredtransmission speed, by use of a transmission path estimation result atthat time, and on the basis of that calculation result, controlstransmission power of the transmitting device 299.

Normally, in Wavelet based multi-carrier communication, a sub carrier,which is using the same band as a band which is used by a partialexisting system (e.g., amateur radio etc.), is made to be of non-usesince it becomes an obstacle to a existing system. By making a subcarrier non-use, a notch is formed.

FIG. 12 is a view of an amplitude spectrum in a DWMC transmissionsystem.

FIG. 12 shows an amplitude spectrum in such a case that a sub carrier,which is using the same band as a band which is used by amateur radio,was made non-use. As shown in FIG. 12, it shows that, by simply makingseveral pieces of sub carriers non-use, a notch of 30 dB or more isformed.

This can be realized since a Wavelet based sub carrier is of a low sidelobe amplitude spectrum. In FIG. 22, shown is a transmission spectrumexample in the DWMC transmission system. A first side lobe of anamplitude spectrum of a sub carrier which is used here is −35 dB.However, when transmission power is increased, a side lobe of each subcarrier is lifted together, and therefore, interference to an existingsystem increases.

In order to prevent this, the transmission path estimator 370 in thisembodiment, so as for the notch to become deeper only by such a portionthat a gain of an amplifier of the transmitting device 299 wasincreased, further makes a sub carrier non-use in the vicinity of them.

In passing, since it has been known in advance how a side lobe of anamplitude spectrum is attenuated, an increase amount of a gain of anamplifier of the transmitting device 299 and the number of sub carrierswhich are made non-use are determined uniquely.

By realizing the suchlike configuration, even if transmission power ofthe transmitting device 299 is increased, there is no such a case thatinfluence to another existing system is increased, and it becomespossible to transmit a signal to a longer way. Furthermore, these thingscan be responded flexibly, simply by making a plurality of sub carriersnon-use.

(Embodiment 18)

The transmission path estimator 370 of a communication apparatus in anembodiment 18 of this invention will be described.

In this embodiment, as a block configuration of a communicationapparatus, used is the block configuration of the communicationapparatus of the conventional system of FIG. 19 or the embodiment 1 or2, and to a transmission path estimation request, transmission pathestimation is assumed to be carried out at a plurality of times. Adynamic range of a receiving device is assumed to be 40 dB.

The number of all sub carriers is assumed to be 300. Here, for ease ofexplanation, it is assumed that a transmission path is a statictransmission path and does not move.

Firstly, in advance, by use of a non-signal zone, a noise level of atransmission path is measured. The noise level is easily obtained by useof a coefficient of an equalizer and a gain of AGC.

Next, normal transmission path estimation (a transmitting device makestransmission with maximum power) is carried out, and a reception signallevel and a CINR value of each sub carrier are estimated. From thereception signal level and a noise level, SNR (signal power to noisepower ratio) of a transmission path is obtained in a simplified manner.As to SNR here, almost SNR that a transmission path is obtained but,CINR, which is obtained at the time of transmission path estimation isdependent on a dynamic range of a receiving device.

On that account, under such an environment that a dynamic range of areceiving device is insufficient, from a relation of an average SNR andan average CINR, it is possible to lower output power of thetransmitting device 299 without deteriorating a transmission speed.

FIG. 13 is a pattern diagram of a received signal revel.

FIG. 13 shows a noise level at the time of no reception signal, a signallevel received by a receiving device when a transmitting device sent asignal with maximum power, and CINR which is obtained at the time oftransmission path estimation. In FIG. 13, in case that a transmittingdevice outputted with maximum power, a receiving device is receivingwith maximum 80 dB μV, minimum 60 dB μV. In addition, CINR, which isobtained at the time of transmission path estimation, becomes maximum 40dB, minimum 20 dB, since a dynamic range of the receiving device is 40dB. As to SNR of a transmission path, it is 60 dB μV at the minimum, butas to CINR, it is simply 20 DB.

This means that transmission power is lost by 40 dB, since a dynamicrange of the receiving device is simply 40 dB. Thus, by use of a gaindifference between SNR of a transmission path and CINR at the time oftransmission path estimation, it is possible to control transmissionpower of a transmitting device without effecting the transmission speed.By this configuration, it is possible to control the transmission powerof the transmitting device based on a gain difference between SNR of atransmission path and CINR obtained at the time of transmission pathestimation, to suppress power consumption of the transmitting device,and to reduce interference to another existing system.

(Embodiment 19)

The transmission path estimator 370 of a communication apparatus in anembodiment 19 of this invention will be described. It is assumed that ablock configuration of a communication apparatus in this embodiment isthe same block configuration of the communication apparatus as in theembodiment 18.

In the method of the embodiment 18, it was possible to suppress powerconsumption of the transmitting device by lowering transmission power,and to reduce interference to another existing system, but it was notpossible to improve transmission speed.

In this embodiment, in addition to the characteristics of the embodiment18, a method of improving a transmission speed of a communicationapparatus will be described.

The transmission path estimator 370 obtains SNR of a transmission pathat the time of transmission path estimation, in the same manner as inthe embodiment ˜18. Calculated is how much a gain can be lowered by, ineach sub carrier, in order to realize a maximum transmission speed andminimum transmission power by use of SNR which was obtained in each subcarrier.

In case that transmission power is not controlled, a multi-value level,which us used in each sub carrier, or information, which corresponds toit, is informed from a receiving device to the transmitting device 299,at the time of transmission path estimation.

Here, in addition to that information, it is designed that informationof a gain which is controlled in each sub-carrier is also informed. Atransmitting device carries out primary modulation of each sub carrierby use of information of a multi-value level, and controls transmissionpower of each sub carrier by use of the gain information.

When this system is applied to a reception signal as shown in FIGS. 13,14, SNR which is obtained in a receiving device becomes almost flat, anda transmission speed can be maximized. It is possible to accuratelyjudge whether a transmission speed is kept maximum, by CINR.

In passing, under such a condition that all sub carriers, which lower again, select a maximum multi-value level, there is no necessity to sendinformation of a multi-value level and information of a gain in a 2divided manner, and it maybe fine if the multi-value level informationor the gain information is informed from a receiving device to atransmitting device. In other words, there is such a necessity that asub carrier, in which there is the gain information, lowers a gain ofthe sub carrier, by use of the gain information on such a matter that amulti-value level is a maximum multi-value level, and a sub carrier inwhich there is the multi-value level information is changed tomulti-values by that information and is made not to control a gain. Inthis regard, however, under the suchlike condition, a reduction range ofa gain becomes small.

By realizing the suchlike configuration, it is possible to improve atransmission speed as compared to the embodiment 18.

(Embodiment 20)

The transmission path estimator 370 of a communication apparatus in anembodiment 20 of this invention will be described. In this embodiment,as a block configuration of a communication apparatus, used is the blockconfiguration of the communication apparatus of the conventional systemof FIG. 19 or the embodiment 1 or 2.

The transmission path estimator 370 is designed to carry outtransmission path estimation at a plurality of times to a transmissionpath estimation request.

Here, for ease of explanation, it is assumed that a transmission path isa static transmission path and does not move.

First of all, normal transmission path estimation (a transmitting devicemakes transmission with maximum power) is carried out. From atransmission path estimation result in a receiving device, only a gainof a sub carrier, which showed a maximum multi-value level, is loweredby only a in a single uniform way. Here, a is obtained from a differenceof threshold values which are used at the time of determining amulti-value level. Also here, for ease of explanation, a use multi-valuelevel is set to 16PAM˜2PAM, and a difference of each threshold value isse to 6 dB in a single uniform way. Here, a is 6 dB. A first timetransmission path estimation result is informed to the transmittingdevice 299 by a multi-value level or information which corresponds toit, and such a fact that a second time transmission path estimation willbe carried out is also informed at the same time. In the secondtransmission path estimation, the transmitting device 299 lowers a gainof only a sub carrier of the maximum multi-value level (here, 16PAM) byonly 6 dB to transmit, and in a receiving device, the secondtransmission path estimation is carried out, and comparing with a firsttime result, if a transmission speed is lowered, transmission pathestimation is finished at the second time, and the last (here, firsttime) transmission path estimation result is informed to thetransmitting device 299 as a result to this time's transmission pathestimation request. If a transmission speed at the second time is fasterthan a transmission speed at the first time, third time transmissionpath estimation is carried out. At the third time, by use of thetransmission path estimation result which was obtained at the secondtime, in the same manner, the transmitting device 299 lowers a gain ofonly a sub carrier of the maximum multi-value level by only 6 dB, totransmit, and in the receiving device, third time transmission pathestimation is carried out.

In this operation, there is such a necessity that the transmittingdevice 299 lowers a gain of a sub carrier whose gain is lowered at boththe first, second time, by only its sum 12 dB.

In short, when N-th time transmission path estimation is carried out,use dare a transmission path estimation result which was obtained at(N-1)-th time and accumulated gains. Similar calculation is repeateduntil a transmission speed comes down, and at such a time point that thetransmission speed came down, transmission path estimation is stopped,and the last result is used as a final result. Here, a concrete examplewill be described by use of FIGS. 13, 15˜17.

FIG. 15 is a pattern diagram of a level of a signal which is received atthe time when gains of sub carriers up to sub carrier numbers 1˜100 werelowered by only 6 dB, and FIG. 16 is a pattern diagram of a level of asignal which is received at the time when gains of sub carriers up tosub carrier number 101˜200 were lowered by only 6 dB, and FIG. 17 is apattern diagram of a level of a signal which is received at the timewhen gains of sub carriers up to sub carrier number 1˜100 were loweredby 18 dB, and gains of sub carriers up to sub carrier number 101˜200 arelowered by 12 dB, and gains of sub carriers up to sub carrier number201˜300 are lowered by only 6 dB.

Firstly, normal transmission path estimation is carried out. It isassumed that FIG. 13 is a pattern diagram of a level of a signal whichwas received. In case that a transmitting device outputted with maximumpower from FIG. 13, a receiving device can receive with maximum 80 dBμV,minimum 60 dBμV. In addition, since a CINR value, which is obtained atthe time of transmission path estimation, becomes maximum 40 dB, minimum20 dB, since a dynamic range of the receiving device is 40 dB. Here,gains of sub carriers up to sub carrier number 1˜100, which areselecting the maximum multi-value level (here, 16PAM), are lowered by 6dB. Here, when second time transmission path estimation is carried out,as shown in FIG. 15, CINR becomes 40 dB, 36 dB, 26 dB. In the samemanner, gains of sub carriers up to sub carrier number 1˜200, whichselected 16PAM, is lowered by 12 dB, 6 dB. Here, when third timetransmission path estimation is carried out, as shown in FIG. 16, CINRbecomes 40 dB, 36 dB, 32 dB. Here, all sub carriers become to select16PAM. Thus, to all sub carriers, gains are lowered by 18 dB, 12 dB, 6dB. In the same manner, when fourth time transmission path estimation iscarried out, 16PAM is selected in all sub carrier in the same manner asin the third time. Here, since a forth time's transmission speed and athird time's transmission speed become the same, processing is finished,and a third time's result is used for communication as a transmissionpath estimation result at this time. In this example, a third time'sspeed and a fourth time's speed become the same by accident, but sincean actual transmission path characteristic is complex, there isgenerally no case that they become the same.

Thus, this processing is continued until such time that a transmissionspeed is deteriorated, and at such a time point that the speed wasdeteriorated, the last result is to be used as a transmission pathestimation result at that time.

In passing, for the purpose of simplifying a system, even incase thattransmission path estimation is used with limitation of 2 times, it ispossible to effectively utilize a dynamic range of a receiving device byonly a dB, as compared to such a case that this system is not used. Inaddition, a gain of only the maximum multi-value level was lowered, butit is possible to obtain the same advantage even without limiting to themaximum multi-value level (e.g., a gain is lowered in a sub carrier of8PAM or more). By the suchlike configuration, transmission pathestimation has to be carried out at a plurality of times, but it ispossible to control transmission power of a transmitting device by asimple produce, in a power line communication apparatus.

Further, in this embodiment, a gain of the transmitting device 299 wascontrolled by use of the CINR value, but it is also possible to carryout power control of the transmitting device 299 by use of SNR of eachsub carrier.

(Embodiment 21)

The transmission path estimator 370 of a communication apparatus in anembodiment 21 of this invention will be described. Here, as a blockconfiguration of a communication apparatus, used is the blockconfiguration of the communication apparatus of the conventional systemof FIG. 19 or the embodiment 1 or 2.

It is assumed that transmission path estimation is carried out at aplurality of times, and at that time, a reception signal level is alsomeasured (noise level measurement is unnecessary). It is assumed that areception level at the time of first transmission path estimation is (a)of FIG. 18. Out of all sub carriers, a MAX level is extracted, and anoffset level is set up, and a gain of a sub carrier, which is receivedwith a level of (MAX level-offset level) or more, is lowered by only Bin a single uniform way. Next, second time transmission path estimationis carried out, and a transmission speed is compared with that of thefirst time, and if a transmission speed has been deteriorated, the lastresult of CINR and gain information are used as a transmission pathestimation result. In case that a transmission speed has been improved,third time is carried out in the same manner. In this way, the same workis repeated until such time that a transmission speed is deteriorated,and in case that the transmission speed was deteriorated, the last CINRresult and gain information are used as a final result. An example isshown in FIG. 18. FIG. 18 is a pattern diagram of a transmission pathestimation characteristic in such a case that a dynamic range isinsufficient.

By the first transmission path estimation, (a) of FIG. 18 is obtained,and here, gains of sub carriers up to sub carrier number 1˜100 arelowered by 18 dB. Next, second time transmission path estimation iscarried out, and from a result of CINR, it is confirmed that atransmission speed has bee improved. Further, third time is carried out,depending upon setup of an offset value, gains of all sub carriers arefurther lowered by 18 dB, and it is judged whether a transmission speedhas been improved or not, and in case that it was deteriorated,transmission path estimation is finished, and the last CINR value andgain information are used as a final result.

In the example of FIG. 18, depending on a value of offset, there existssuch a case that a second time's speed and a third time's speed becomethe same by accident, but since an actual transmission pathcharacteristic is complex, we think that there is generally no such acase that they become the same. This, this processing is continued untilsuch time that a transmission speed is deteriorated, and at such a timepoint that the speed was deteriorated, the last result is to be used asa transmission path estimation result at that time. Depending on SNR ofa transmission path, a characteristic of a sub carrier whose gain waslowered may be deteriorated, but in case of such a transmission paththat a dynamic range of a receiving device is insufficient as in FIG.18, thanks to such a fact that a gain of a certain sub carrier waslowered, insufficiency of a dynamic range of entirety is alleviated, andas a result, a transmission speed may be improved. In a transmissionpath which shows a characteristic as in (a) of FIG. 18, this system isvery useful.

In short, in such a case as in FIG. 18, by significantly lowering a gainof a sub carrier in which a reception level is large, a transmissionspeed of an entire system is improved. In a power line transmissionpath, since an attenuation characteristic and a noise characteristic arecomplex, we thing that the suchlike method is useful. In passing, sinceit is troublesome to carry out transmission path estimation at aplurality of times, transmission path estimation is limited to 2 times,and as a simplified manner, a sub carrier in which a reception level is(MAX level-offset level) or more, is made non-use daringly, and secondtime transmission path estimation is carried out and it may be confirmedwhether a speed has been improved. Or, by drastically lowering a gain,but not non-use, CINR maybe determined by second time processing. Byrealizing the suchlike configuration, it is possible to improvetransmission speed deterioration due to insufficiency of a dynamic rangeof a receiving device, and even in a complex transmission path, it ispossible to improve a transmission speed.

(Embodiment 22)

As a block configuration of a communication apparatus in an embodiment22 of this invention, used is the block configuration of thecommunication apparatus of the conventional system of FIG. 19 or theembodiment 1 or 2.

A frame configuration example of the communication apparatus in thisembodiment is shown in FIG. 26. FIG. 26 is a view which shows the frameconfiguration example of the communication apparatus in the embodiment22 of this invention.

In FIG. 26, this frame configuration shows data which is transmittedtoward a receiving device, on the basis of information which thetransmitting device 299 obtained from the transmission path estimator370 of a receiving device.

In the figure, PRE shows a preamble signal which is used insynchronization processing, equalization processing etc. of a receivingdevice, and SYNC shows a SYNC signal which identifies a data start, andTMI shows a signal which shows information based upon a transmissionpath estimation result, and FC shows a frame control signal, and PLshows an information signal.

The information which is based upon a transmission path estimationresult of TMI may be a result itself which was estimated by thetransmission path estimator 370 of a receiving device, or informationwhich defines modulation and demodulation, which are use in transmissionand reception, on the basis of estimation.

In a normal frame configuration, as shown in the following, a controlsignal (PRE and SYNC) is located at the forefront, and thereafter, theinformation signal follows. In this embodiment, transmission pathestimation information is placed at a forefront portion of theinformation signal. In the example of FIG. 26, it is placed before SYNC,and before FC1. By realizing the suchlike configuration, since itbecomes possible to process the TMI signal in the beginning, it ispossible to quickly carry out processing of the information signal byuse of information of TMI.

(Embodiment 23)

As a block configuration of a communication apparatus in an embodiment23 of this invention, considered is the same block configuration as thatof the communication apparatus which was disclosed in the embodiment 22.

Here, diversity (frequency diversity, time diversity etc.) processing iscarried out to transmission path estimation result information, and theinformation is used as the TMI signal. However, since an informationamount of a normal transmission path estimation result is increased, ifit is detailed, by that much, when diversity processing with high gainis applied to a large amount of information, transmission efficiency islowered (there is such a possibility that the TMI signal becomes severalseveral dozen symbols). A high resistance property is required for theTMI signal. On that account, the high gain diversity processing isdesired to be carried out to the TMI signal, only at such time thattransmission path estimation was carried out, detailed transmission pathestimation result information is exchanged in a communication apparatusas the information signal, and that information is stored in a memoryetc., and in a normal communication state, transmitted is onlyinformation (INDEX etc.) from which a location, in which thatinformation is stored, is known.

Since an amount of information which is necessary at this time islessened (normally, several bits), it becomes possible to improve adiversity gain to a large extend, without lowering transmissionefficiency. In passing, as a method of obtaining a high gain to the TMIsignal, there is error correction, other than diversity, but high gainerror correction is generally of large system delay. When processing ofthe TMI signal is delayed due to system delay, it has an impact onperformance of an entire system, and therefore, application isdifficult.

In this embodiment, there is only the high gain diversity processing tothe TMI signal, and since high gain error correction is not used, systemdelay is small. By realizing the suchlike configuration, it is possibleto generate the TMI signal in which system delay is small, and which hasa high resistance property.

In passing, a series of systems were described as to such a case thatthey were applied to power line communication, and in addition,multi-carrier communication was described as to such a case that waveletbased OFDM was used. However, this system is applicable not only to thewavelet based OFDM, but also to muti-carrier communication whichrealizes another low side lobe spectrum, by use of OFDM/OQAM (in thiscase, a multi-value level of a primary modulation system is MQAM: M is amulti-value number), Filtered OFDM, Filterred Mutitone systems etc.

In addition, also as a transmission path, it is not limited to atransmission path of a power line, and it is possible to apply to adigital communication apparatus etc. which utilizes a power line as atransmission path.

A communication apparatus, which relates to this invention, becomespossible to follow sufficiently to various fluctuations of atransmission path such as a power line, and as a power linecommunication apparatus, or by applying to a high speed communicationapparatus of another transmission path, it is useful.

This application is based upon and claims the benefit of priority ofJapanese Patent Application No. 2003-288747 filed on Jul. 30, 2004, thecontents of which are incorporated herein by reference in its entirety.

1. A communication apparatus which carries out multi-carrier modulationprocessing, comprising a receiving device including: ananalog-to-digital converter which converts an analog signal which wasreceived, into a digital signal; a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal; acarrier detector for detecting the reception signal; a synchronouscircuit for being synchronized with the reception signal; an equalizerfor compensating a distorted signal due to influence of a transmissionpath; a noise detector which detects presence or absence of narrow-bandnoise in each sub carrier band by use of a signal which was converted bysaid converter; a transmission path estimator which determines amulti-value level of primary modulation which is used by each subcarrier of a symbol mapper in a transmitting device, by use of a signalwhich is outputted from said equalizer and information of presence orabsence of the narrow-band noise which is outputted from said noisedetector; and a judging unit which carries out judgment by use of thesignal which is outputted from said equalizer.
 2. The communicationapparatus as set forth in claim 1, wherein said noise detector judges,in case that an output of the signal which was converted by saidconverter exceeds a predetermined value, that it is narrow-band noise.3. The communication apparatus as set forth in claim 1 or 2, wherein incase that it was judged by said noise detector that there is noise, saidtransmission path estimator makes a judged sub carrier non-use.
 4. Thecommunication apparatus as set forth in claim 1, wherein the receivingdevice further has an AGC circuit which automatically adjust a gain ofthe reception signal, and said noise detector judges, in case thatfluctuation of the gain exceeded a predetermined value, by an output ofsaid AGC circuit, that there is wide-band noise.
 5. The communicationapparatus as set forth claim 1 or 4, wherein in case of using a powerline as the transmission path, said transmission path estimator carriesout transmission path estimation for 1 cycle portion of a power supplycycle, by use of a transmission path estimation frame, continuouslyduring a period of a power supply cycle, and takes hold of which timingfluctuation due to noise and transmission path fluctuation weregenerated at, and in that zone, it is made to not send out a signal, orit is made to lower a multi-value level of primary modulation of thesymbol mapper of the transmitting device, or frequency diversity or timediversity or both diversities are used.
 6. The communication apparatusas set forth in claim 1 or 4, wherein said transmission path estimatoris used even if there is fluctuation, in case that influence offluctuation is smaller than a certain threshold value in each subcarrier.
 7. A communication apparatus which carries out multi-carriermodulation processing, comprising a receiving device including: ananalog-to-digital converter which converts an analog signal which wasreceived, into a digital signal; a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal; acarrier detector for detecting a transmission signal transmitted from atransmitting device; a synchronous circuit for being synchronized withthe reception signal; an equalizer for compensating a distorted signaldue to influence of a transmission path; a judging unit which carriesout judgment by use of the signal which is outputted from saidequalizer; and a transmission path estimator which determines amulti-value level of primary modulation which is used by each subcarrier of a symbol mapper in the transmitting device, by use of asignal which is outputted from said equalizer and a judgment value whichis outputted from said judging unit.
 8. The communication apparatus asset forth in claim 7, wherein said transmission path estimator carriesout transmission path estimation accurately, even in case that thenumber of symbols in a data frame is smaller than the number of symbolsnecessary for estimating a transmission path.
 9. The communicationapparatus as set forth claim 7, wherein said transmission path estimatoris made to be able to carry out transmission path estimation in a dataframe, even in a sub carrier which was judged to be non-use in atransmission path estimation exclusive use frame.
 10. A communicationapparatus which carries out multi-carrier modulation processing,comprising a receiving device including: an analog-to-digital converterwhich converts an analog signal which was received, into a digitalsignal; a converter which generates an in-phase signal and a orthogonalsignal by converting a reception signal; a carrier detector fordetecting the reception signal; a synchronous circuit for beingsynchronized with the reception signal; an equalizer for compensating adistorted signal due to influence of a transmission path; a transmissionpath estimator which determines a multi-value level of primarymodulation which is used by each sub carrier of a symbol mapper in atransmitting device, by use of a result of transmission path estimation;and a judging unit which carries out judgment by use of the signal whichis outputted from said equalizer, wherein said transmission pathestimator carries out plural times of transmission path estimations to atransmission path estimation request.
 11. The communication apparatus asset forth in claim 10, wherein said transmission path estimator combinesa transmission path estimation result and modification of a thresholdvalue which is used in said transmission path estimator.
 12. Thecommunication apparatus as set forth in claim 10, wherein saidtransmission path estimator combines plural results of estimation andretransmission, and makes a sub carrier whose fluctuation is large,non-use, to a result which was obtained in each sub carrier or selects aminimum value among results which were obtained.
 13. The communicationapparatus as set forth in claim 10, wherein the communication apparatususes a power line as a transmission path, and said transmission pathestimator is designed to carry out 2 times of transmission pathestimations to a transmission path estimation request, and as to atleast 1 time among 2 times of transmission path estimations,transmission path estimation is carried out without being synchronizedwith transmission path fluctuation which was synchronized with a powersupply cycle.
 14. The communication apparatus as set forth in claim 10,wherein the communication apparatus uses a power line as a transmissionpath, and said transmission path estimator divides a frame in case thatit judged that a transmission path is fluctuated periodically.
 15. Acommunication apparatus which carries out multi-carrier modulationprocessing, comprising a receiving device including: ananalog-to-digital converter which converts an analog signal which wasreceived, into a digital signal; a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal; acarrier detector for detecting the reception signal; a synchronouscircuit for being synchronized with the reception signal; an equalizerfor compensating a distorted signal due to influence of a transmissionpath; a transmission path estimator which determines a multi-value levelof primary modulation which is used by each sub carrier of a symbolmapper in a transmitting device, by use of a result of transmission pathestimation; and a judging unit which carries out judgment by use of thesignal which is outputted from said equalizer, wherein said transmissionpath estimator carries out transmission path estimation by a state of atransmission path and a transmission data amount which is requested to atransmitting device.
 16. The communication apparatus as set forth inclaim 15, wherein said transmission path estimator carries outtransmission path estimation by a state of a transmission path and atype of an application of data which is desired to be transmitted.
 17. Acommunication apparatus which carries out multi-carrier modulationprocessing, comprising a receiving device including: ananalog-to-digital converter which converts an analog signal which wasreceived, into a digital signal; a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal; acarrier detector for detecting a transmission signal transmitted from atransmitting device; a synchronous circuit for being synchronized withthe reception signal; an equalizer for compensating a distorted signaldue to influence of a transmission path; a transmission path estimatorwhich determines a multi-value level of primary modulation which is usedby each sub carrier of a symbol mapper in the transmitting device, byuse of a result of transmission path estimation; and a judging unitwhich carries out judgment by use of the signal which is outputted fromsaid equalizer, wherein said transmission path estimator carries outtransmission path estimation in which group delay of a transmission pathwas mitigated.
 18. A communication apparatus which carries outmulti-carrier modulation processing, comprising a receiving deviceinclduing: an analog-to-digital converter which converts an analogsignal which was received, into a digital signal; a converter whichgenerates an in-phase signal and a orthogonal signal by converting areception signal, a carrier detector for detecting the reception signal;a synchronous circuit for being synchronized with the reception signal;an equalizer for compensating a distorted signal due to influence of atransmission path; a transmission path estimator which determines amulti-value level of primary modulation which is used by each subcarrier of a symbol mapper in a transmitting device, by use of a resultof transmission path estimation; and a judging unit which carries outjudgment by use of the signal which is outputted from said equalizer,wherein said transmission path estimator carries out transmission pathestimation by setting up redundancy to transmission data from atransmitting device, in case that a desired transmission speed is notobtained.
 19. A communication apparatus which carries out multi-carriermodulation processing, comprising a receiving device including: ananalog-to-digital converter which converts an analog signal which wasreceived, into a digital signal; a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal; acarrier detector for detecting the reception signal; a synchronouscircuit for being synchronized with the reception signal; an equalizerfor compensating a distorted signal due to influence of a transmissionpath; a transmission path estimator which determines a multi-value levelof primary modulation which is used by each sub carrier of a symbolmapper in a transmitting device, by use of a result of transmission pathestimation; and a judging unit which carries out judgment by use of thesignal which is outputted from said equalizer, wherein said transmissionpath estimator, in case that, when a desired transmission speed is notsatisfied, a transmitting device tries to satisfy the desiredtransmission speed by increasing transmission power, makes a sub carrierin the vicinity of a use band of another existing system, non-use, inproportion to a gain increase portion of transmission power.
 20. Acommunication apparatus which carries out multi-carrier modulationprocessing, comprising a receiving device including: ananalog-to-digital converter which converts an analog signal which wasreceived, into a digital signal; a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal; acarrier detector for detecting the reception signal; a synchronouscircuit for being synchronized with the reception signal; an equalizerfor compensating a distorted signal due to influence of a transmissionpath; a transmission path estimator which determines a multi-value levelof primary modulation which is used by each sub carrier of a symbolmapper in a transmitting device, by use of a result of transmission pathestimation; and a judging unit which carries out judgment by use of thesignal which is outputted from said equalizer, wherein said transmissionpath estimator controls transmission power of a transmitting device, byuse of CINR (Carrier power to (Interference-plus-Noise) power Ratio)which is obtained by use of a signal which is outputted from saidequalizer, and SNR (signal power-to-noise power ratio) of a transmissionpath, which is obtained after said conversion.
 21. A communicationapparatus which carries out multi-carrier modulation processing,comprising a receiving device including: an A/D converter which convertsan analog signal which was received, into a digital signal; a converterwhich generates an in-phase signal and a orthogonal signal by convertinga reception signal; a carrier detector for detecting the receptionsignal; a synchronous circuit for being synchronized with the receptionsignal; an equalizer for compensating a distorted signal due toinfluence of a transmission path a transmission path estimator whichdetermines a multi-value level of primary modulation which is used byeach sub carrier of a symbol mapper in a transmitting device, by use ofa result of transmission path estimation; and a judging unit whichcarries out judgment by use of the signal which is outputted from saidequalizer, wherein said transmission path estimator controls a gain ofeach sub carrier of a transmitting device, by use of SNR of atransmission path, which is obtained by use of a reception signal aftersaid conversion, so as to realize a maximum transmission speed andminimum transmission power.
 22. A communication apparatus which carriesout multi-carrier modulation processing, comprising a receiving deviceincluding: an analog-to-digital converter which converts an analogsignal which was received, into a digital signal; a converter whichgenerates an in-phase signal and a orthogonal signal by converting areception signal; a carrier detector for detecting the reception signal;a synchronous circuit for being synchronized with the reception signal;an equalizer for compensating a distorted signal due to influence of atransmission path; a transmission path estimator which determines amulti-value level of primary modulation which is used by each subcarrier of a symbol mapper in a transmitting device, by use of a resultof transmission path estimation; and a judging unit which carries outjudgment by use of the signal which is outputted from said equalizer,wherein said transmission path estimator controls a gain of each subcarrier of a transmitting device, by use of CINR which is obtained byuse of a signal which is outputted from said equalizer.
 23. Acommunication apparatus which carries out multi-carrier modulationprocessing, comprising a receiving device including: ananalog-to-digital converter which converts an analog signal which wasreceived, into a digital signal; a converter which generates an in-phasesignal and a orthogonal signal by converting a reception signal; acarrier detector for detecting the reception signal; a synchronouscircuit for being synchronized with the reception signal; an equalizerfor compensating a distorted signal due to influence of a transmissionpath; a transmission path estimator which determines a multi-value levelof primary modulation which is used by each sub carrier of a symbolmapper in a transmitting device, by use of a result of transmission pathestimation; and a judging unit which carries out judgment by use of thesignal which is outputted from said equalizer, wherein said transmissionpath estimator extracts a MAX level out of all sub carriers by use of areception level which is obtained by use of a reception signal aftersaid conversion, to set up an Offset level, and to lower a gain of a subcarrier whichisbeingreceivedwithalevelof (MAX level-offsetlevel) ormore, with only uniformity β, or to make those sub carriers non-use. 24.A communication apparatus comprising: a receiving device having atransmission path estimator, and a transmitting device which determineda transmission data frame by use of information which is based upon atransmission path estimation result which is transmitted from thereceiving device, wherein said transmitting device transmits such atransmission data frame that the information, which was obtained fromsaid transmission path estimator and is based upon a transmission pathestimation result, was placed at the forefront.
 25. The communicationapparatus as set forth in claim 24, wherein said transmitting deviceplaces the information, which is based upon a transmission pathestimation result, at the forefront of a information signal, and carriesout diversity processing to the information which is based upon atransmission path estimation result.
 26. A communication method whichcarries out multi-carrier modulation processing, comprising: ananalog-to-digital converting step which converts an analog signal whichwas received, into a digital signal; a converting step which generatesan in-phase signal and a orthogonal signal by converting a receptionsignal; a carrier detecting step for detecting the reception signal; asynchronizing step for being synchronized with the reception signal; anequalizing step for compensating a distorted signal due to influence ofa transmission path; a noise detecting step which detects presence orabsence of narrow-band noise in each sub carrier band by use of a signalwhich was converted by said converter; and a transmission pathestimating step which determines a multi-value level of primarymodulation which is used by each sub carrier of a symbol mapper in atransmitting device, by use of a signal which is outputted from saidequalizing step and information of presence or absence of thenarrow-band noise which is outputted from said noise detecting step.